Radiation image read-out apparatus, radiation image recording method and apparatus, stimulable phosphor sheet, and cassette

Abstract

In a radiation image read-out apparatus, a phosphor sheet (70), represented by the formula Gd 2 O 2 S:Tb 3+ , is located facing a stimulable phosphor sheet (10) in such a manner that when it is exposed to x-rays (44) it produces fluorescence (71) having a wavelength that fall within the stimulation wavelength range of the stimulable phosphor. When the stimulable phosphor sheet (10) is exposed to the fluorescence (71), part of the energy stored on the layer of stimulable phosphor during its exposure to the x-rays (44) is released. In this manner, the stimulable phosphor sheet (10) is approximately simultaneously subjected to the operation for recording the radiation image and the operation for slightly erasing the energy store thereon during its exposure to the x-rays (44).

We claim: 
     
       1. A radiation image recording method wherein a stimulable phosphor sheet provided with a layer of a stimulable phosphor is exposed to radiation, which carries information about an image, and the image is thereby stored on the stimulable phosphor sheet, said stimulable phosphor exhibiting such properties that, when it is exposed to radiation and is then exposed to stimulating rays, it emits light in proportion to the amount of energy stored thereon during its exposure to the radiation, the radiation image recording method comprising the steps of:   i) locating a layer of a phosphor such that it faces the layer of said stimulable phosphor, said phosphor exhibiting such properties that, when it is exposed to the radiation, it produces fluorescence having wavelengths falling within the stimulation wavelength range of said stimulable phosphor, and   ii) thereafter irradiating the radiation to said stimulable phosphor sheet.   
     
     
       2. A radiation image recording method as defined in claim 1 wherein said stimulable phosphor is represented by the formula BaFX:Eu 2+ , wherein X is a halogen. 
     
     
       3. A radiation image recording method as defined in claim 2 wherein said phosphor, which produces the fluorescence, is represented by the formula Gd 2  O 2  S:Tb 3+ . 
     
     
       4. A radiation image recording method as defined in claim 2 wherein said phosphor, which produces the fluorescence, is represented by the formula Y 2  O 2  S:Tb 3+ . 
     
     
       5. A radiation image recording method as defined in claim 1 wherein said radiation is X-rays. 
     
     
       6. A radiation image recording method as defined in claim 1 wherein said stimulating rays are a laser beam. 
     
     
       7. A stimulable phosphor sheet provided with a layer of a stimulable phosphor which exhibits such properties that, when it is exposed to radiation and is then exposed to stimulating rays, it emits light in proportion to the amount of energy stored thereon during its exposure to the radiation, wherein the improvement comprises the provision of a layer of a phosphor, which is located such that it faces the layer of said stimulable phosphor and which exhibits such properties that, when it is exposed to the radiation, it produces fluorescence having wavelengths falling within the stimulation wavelength range of said stimulable phosphor.   
     
     
       8. A stimulable phosphor sheet as defined in claim 7 wherein said phosphor which produces the fluorescence is dispersed in a binder, which is used to hold said stimulable phosphor on a sheet-like substrate. 
     
     
       9. A stimulable phosphor sheet as defined in claim 7 wherein the layer of said phosphor which produces the fluorescence is formed independently of the stimulable phosphor layer and located so that it is close to or in close contact with the stimulable phosphor layer. 
     
     
       10. A stimulable phosphor sheet as defined in claim 7 wherein said stimulable phosphor is represented by the formula BaFX:Eu 2+ , wherein X is a halogen. 
     
     
       11. A stimulable phosphor sheet as defined in claim 10 wherein said phosphor, which produces the fluorescence, is represented by the formula Gd 2  O 2  S:Tb 3+ . 
     
     
       12. A stimulable phosphor sheet as defined in claim 10 wherein said phosphor, which produces the fluorescence, is represented by the formula Y 2  O 2  S:Tb 3+ . 
     
     
       13. A stimulable phosphor sheet as defined in claim 7 wherein said radiation is X-rays. 
     
     
       14. A stimulable phosphor sheet as defined in claim 7 wherein said stimulating rays are a laser beam. 
     
     
       15. A cassette for housing a stimulable phosphor sheet provided with a layer of a stimulable phosphor which exhibits such properties that, when it is exposed to radiation and is then exposed to stimulating rays, it emits light in proportion to the amount of energy stored thereon during its exposure to the radiation, wherein the improvement comprises the provision of a layer of a phosphor, which is located such that it faces the surface of said stimulable phosphor sheet housed in said cassette, said phosphor exhibiting such properties that, when it is exposed to the radiation, it produces fluorescence having wavelengths falling within the stimulation wavelength range of said stimulable phosphor.   
     
     
       16. A cassette as defined in claim 15 wherein said stimulable phosphor is represented by the formula BaFX:Eu 2+ , wherein X is a halogen 
     
     
       17. A cassette as defined in claim 16 wherein said phosphor, which produces the fluorescence, is represented by the formula Gd 2  O 2  S:Tb 3+ . 
     
     
       18. A cassette as defined in claim 16 wherein said phosphor, which produces the fluorescence, is represented by the formula Y 2  O 2  S:Tb 3+ . 
     
     
       19. A cassette as defined in claim 15 wherein said radiation is X-rays. 
     
     
       20. A cassette as defined in claim 15 wherein said stimulating rays are a laser beam.